controlling dc motor speed

[tmdar]

Hi,
I am using two dc motors which can operate upto 9V and can consume upto 5amps(stall current) I am using DAQ 6024E and labview 7.1 --- I want to controll the speed of these motors like starting from some zero velocity to maximum and then reducing back to zero-- how can I do that with the help of labview.

Thanks in advance

[Jochen]

For real motion control you need a closed loop system and a deterministic control algorithm. The best solution is the use of NI motion control boards that integrate perfectly into LabVIEW. These boards run the control algorithm onboard in a real-time environment.

It's not a good idea to run any time-critical control algorithm on a Windows system as this OS is non deterministic. If your requirements for the quality of the control are very very low you could try to simply output voltage ramps with your 6024E and run in open loop mode but as said this won't result in a good control behavior.

Another option would be the use of LabVIEW Real-Time on a PXI system or on a desktop PC (works only under certain circumstances; refer to the last link) but a motion control board will be a much better and cheaper option.

Best regards,

Jochen Klier
National Instruments Germany

[Brian_Beal]

Depending on how accurate your speed needs to be, you could use standard DC motor controllers that have an analog input for speed control. You could then use the analog outputs on the DAQ to control speed.

[Jochen]

This option will work as long as you don't need to control the position but it will work for velocity control.

Jochen Klier
National Instruments Germany

[tmdar]

Hi,
I am intrested in velocity controll eg I would like to make motor travell from point A to B with zero rpm to some higher rpm(may to max that motor can go)
motor is 9V dc ( item # 1205 at www.hobbyengineering.com)

infact I want to study the slip which is taking place under the track of my robot. On top of my robot is range sensor which is giving me the range from object and have encoder on the sprocket so it can tell me the rpm of the sprocket.

I initially had micro dual motor controller from pololu but it can handle 1 amps per motor so it is of no use to me now since my motors stall current is 5 amps.

So I want to start from rest go some distance with zero velocity gain momentum gradually and then stop.

Which motor controller are you suggesting.

Thanks

[ryanm]

Hi,

National Instruments makes the MID 7652 Drive, which can output up to 5 Amps. When used in conjuction with the PCI-7342 Motion Controller, you would be able to control your motor. However, in your particular case, this setup seems like overkill. You might want to look into the Motor Mind C by Parallax (www.parallax.com). This motion controller has a serial connection, so you would be able to use LabVIEW. The motor can be controlled through VISA commands and the 6024E can read the quadrature encoder position.

[tmdar]

Hi
you have given me good ideas but very expensive and I am doing my projetc all by my self.
Ni boards are for servo motors and stepper motors-- mind set c does not have enough amperage ( 1.5 amps) for my motors(stall current 5 amps or atleast motor controller that can handle upto 3 amps for each motor.

I need some more specifics about DC motor controller and some more ideas


Thanks

[ryanm]

Again, we recommend using the MID 7652 Drive and the PCI-7342 Motion Controller. As much as I would like to help you with your project, my expertise outside these products is somewhat limited. As a starting point, you may want to look at H-bridge MOSFETs. Many of these chips would be able to output 5+ amps.

[Brian_Beal]

Try looking at this: http://www.pololu.com/products/pololu/0392/

[tmdar]

Hi,
I used micro dual motor controller from Pololu and I discussed this new 3 amp controler with them aswell but I t does not suit my application as it is under rated for my two motors. They are introducing new 30 amp motor controller in late june.
Which is lttle late for me.
Lets see what all options do I have
Thanks